Precursor structure, distribution and possible functions of pigment-dispersing hormone (PDH) in the terrestrial isopod Armadillidium vulgare (Latreille)

Jul 20, 2010Journal of insect physiology

Production, spread, and possible roles of pigment-dispersing hormone in the land-dwelling woodlouse Armadillidium vulgare

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Abstract

A cDNA encoding the pigment-dispersing hormone (PDH) was cloned from the pill bug, Armadillidium vulgare, consisting of 529 base pairs.

The PDH peptide includes a 26 amino acid signal peptide and an 18 amino acid mature peptide.
Sequence analysis shows 55-77% identity of AvPDH to crustacean β-PDHs and insect PDF peptides.
Transcript expression is strong in the brain and weak in the ventral nerve cord, with no detection in the intestinal tract.
Western blot analyses indicate increased PDH-like antigen expression at night.
Immunohistochemical analysis reveals PDH-like reactivity in specific brain regions, but not in the pseudofrontal organ.
Co-localization of PDH with clock proteins CLK and CYC suggests a potential role in circadian rhythms.

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Pigment-dispersing hormone (PDH) is an 18 amino acid neuropeptide that induces pigment migration in Decapoda and serves as a circadian neurotransmitter in the locomotor activity rhythm in Drosophila. In this study, a cDNA encoding PDH was cloned from adult brains of the pill bug, Armadillidium vulgare (Av). The cDNA comprising 529 bp encodes a peptide (AvPDH) that consists of a putative 26 amino acid signal peptide, and a 34 amino acid PDH-precursor-related peptide containing an 18 amino acid mature peptide. The peptide shows a high sequence identity (55-77%) to crustacean β-PDHs and insect PDFs. The tissue-specific expression pattern was examined by reverse transcription PCR. The transcript is expressed in the brain strongly and ventral nerve cord weakly, but the signal was not detected in the intestinal tract. A similar expression profile appeared in Western blot analyses. Western blot analyses with timed samples showed more intense expression of PDH-like antigen at night. PDH-like immunohistochemical reactivity (PDH-ir) was detected in the optic lobe, anteromedian protocerebrum, accessory lobe, tritocerebrum, and suboesophageal ganglion but the reactivity was faint or nil in the pseudofrontal organ (sinus gland). These results were substantiated by in situ hybridization. Co-localization using anti-Gryllus bimaculatus (Gb)-PDF, anti-Bombyx mori (Bm)-CLK, and anti-Bm-CYC showed a co-localization of these antigens in the optic lobe and SOG. The results provide the first structural and immunocytochemical identification of PDH neurons in terrestrial isopods, and the co-localization of PDH with CLK and CYC supports its possible involvement in circadian clock. A day/night rhythm of PDH content is also a new feature.

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Precursor structure, distribution and possible functions of pigment-dispersing hormone (PDH) in the terrestrial isopod Armadillidium vulgare (Latreille)

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